Centrifugal pump



Jan. 2, 1951 c. M. BoLsTER CENTRIFUGAL PUMP Filed April l2, 1945 8 Sheets-Sheet 1 l m @s i n Q3 l5 lg "It I l1 El 1 I l@ L u@ Q4-'5. Fs W n@ 1 @o M "i R2 g 4 r2 !NVENTOR @dwf/@0.51pm

BYWLMQ ATTORNEY C. M. BOLSTER CENTRIFUGAL PUMP Jan. 2, 1951 Filed April l2, 1945 ATTORNEY C. M. BOLSTER CENTRIFUGAL PUMP Jan. 2, 1951 8 Sheets-Sheet 5 Filed April 12, 1945 @N mx wm. Q

Nw om NVENTOR ATTORNEY 8 Sheets-Sheet 4 Wwf/5% wf/L L ATTORNEY C. M. BOLSTER CENTRIFUGAL PUMP Jan; 2, `1951 Filed April l2, 1945 Jan. 2, 1951 c. M. BoLsTER 2,535,026

CENTRIFUGAL PUMP Filed April 12, 1945 s sheets-sheet s INVENTOR 5M/m @y 50m, Bf @WLM ATTORNEY 8 Sheets-Sheet 6 l BY @am LJ.

C. M. BOLSTER CENTRIFUGAL PUMP :ummllnlmiumn Jan. 2, 1951 Filed April 12, 1945 Jan. 2, 1951 "c:. M. HOLSTER CENTRIFUGAL PUMP 8 Sheets-Sheet '7 Filed April l2, 1945 BY im o L-TORNE C. M. BOLSTER CENTRIFUGAL PUMP Jan. 2, V1951 8 Sheets-Sheet 8 Filed April l2, 1945 SQ lfm/M f WN QN Mmmm NQ QN Patented Jan. 2, 1951 UNITED STATES PATENT OFFICE 16 Claims. (Cl. 103--109) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) This invention relates to centrifugal pumps and it has a particular relation to pumps of the multi-stage type.

The principal object of the invention is the provision f a centrifugal pump in which the diameter of the pressure chamber or container is only a fraction of the effective diameter of the pump rotors or impellers about their common axis of rotation which results in a great reduction in weight and wall thickness of the chamber for any given pressure.

Another object of the invention is the provision of a pump embodying a plurality of oppositely rotating rotors for causing a direct flow of the iluid through successive stages with a resultant multi-stage arrangement in a relatively small volumetric space.

A further object of the invention is the provision of a pump of the character described in which the several oppositely rotating impellers move about instantaneously xed centers of rotation located in the circumferences thereof, Whereby the flow of fluid from one impeller to another caused by centrifugal force will be in a direction diametrical of the impeller from such instantaneous fixed point of rotation to a circumferentially disposed point diametrically opposite thereto and the flow of fluid through adjacent impellers being in opposite directions notwithstanding the rotation of the several impellers about their common axis.

' Still another object of the invention is the provision of a centrifugal pump embodying one or more units mounted for revolution about a common axis and each having a plurality of coaxially arranged oppositely rotating impeller elements or rotors the arrangement being such that the centrifugal force generated by the several impellers is accumulative as the iluid passes from stage to stage.

A still further object of the invention is the provision of a pump wherein the radial travel of the medium being pumped is extremely small although the velocity and pressure rise is relatively great.

. Another object of the invention is the provision `of a centrifugal pump embodying a plu.- rality of individual pump units arranged symmetrically about a central shaft and connected invseries whereby a high number of pressure stages may be employed within a relatively small space.

Still another object of the invention is the provision of a centrifugal pump embodying a plurality of centrifugal pump assemblies mounted for revolution about a common central axis and which are adjusted radially with re` spect to said axis so as to obtain a variable pressure delivery with any given rate of rotation.

In order to make the invention more clearly understood there are shown in the accompanying drawings, means for carrying the invention into practical effect, without limiting the improvements in their useful application to the particular constructions and arrangements which, for the purpose of explanation, have been made the subject of illustration.

In the accompanying drawings:

Fig. 1 is a side elevational view of multi-stage centrifugal pump constructed in accordance with the invention;

Fig. 2 is an end elevational view of the pump structure shown in Fig. 1 as viewed from the delivery or right hand end of Fig l;

Fig. 3 is an enlarged view partly in plan and partly in horizontal step section taken substantially on the line 3--3 of Fig. 2;

Fig. 4 is a vertical transverse sectional view through the pump units taken on line 2 4 of Fig. 1;

Fig. 5 is a view similar to Fig. 4 but taken on line 5--5 of Fig. 1;

Fig. 6 is an enlarged fragmentary vertical longitudinal sectional view of both ends of the pump; l

Fig. '7 is an enlarged fragmentary transverse sectional view of the pressure varying mechanism taken on line 'l-l of Fig. 1;

Fig. 8 is an exploded perspective view of one of the impeller o r rotor mechanisms of the Dump;

Fig. 9 is a diagrammatic end elevational view of a centrifugal pump constructed with five inter-communicating pump units;

Figs. l0 and 11 are vector diagrams illustrating the diametrical ow of the fluid medium through the oppositely rotating impellers of the pump.

Fig. 12 is a diagrammatic view of two adjacent impellers or rotors circu-mferentially offset relative to one another and illustrating the diametrical iiow or the fluid medium under centrifugal action when the impellers are moved about an instantaneous xed point in space.

Fig. 13 is a longitudinal cross sectional view illustrating a modied form of the invention.

Fig. 14 is a cross sectional view taken on the line Ill- I4 of Figure 13 and Figs. l5 and 16 illustrate diagrammatically still further modified forms of the invention.

Referring to the drawings, the present invention comprises three or more housings l5, each provided with axially alined trunnions or stud shafts Ii' and i2 disposed eccentrically with ree spect to the housing at opposite ends thereo which are pivotally mounted in bearings E and Irl on arms I and I5 of spiders Il and I8. Each of the bearings I3 and Ill are provided with double shaft seals I9 and 2i? respectively. These spiders are formed on the ends of the shafts 2E and 22 which are journalled in n bearings 23 and 2d carried end support.; castings 25 and 25 formed on or secured to a base plate 2l.

One end of each of the housings Iii is formed with an integral head 28, provided with a shaft seal 29 and the other is closed by a removable head 30, provided with a shaft seal SI. Rotatably mounted within a bore 32 of the housing IU is an impeller cage 33 (see Figs. S and 8) which contains a plurality of alternately arranged oppositely rotatable impellers fili and 55. The impellers 3d comprise awall 35a, blades 35:1), and a plurality of peripheral tongues or keys which are adapted to project into slots Si formed in the cage 33 so as to rotate therewith. The iinpellers 35 on the other hand have smooth peripheries and are free to rotate independently of the cage 33 and the impellers 3d, and comprise a Wall 35a, blades 3517 and keyseformed in hubs 39 thereof. The keys 35 are adapted to engage a keyway tu formed in the shaft llI sc as to rotate therewith. This shaft extends coaxially through the housing and is journalled intermediate its end in a friction-less bearing d2 mounted in the integral head 43 of the impeller cage and has keyed thereto a gear @il which is held against displacement by a lock nut 5. The other end is journalled in a friction-less bearing te mounted in a removable driving head Il? of the impeller cage. The driving head il forms an end closure for the impeller cage and is keyed thereto by peripheral tongues or keys 118 which project into the slots 3l thereof and is adapted to drive the impeller cage and its associated impellers 3d independ'ently of the impellers 55. This driving head is provided with a boss i9 which ig journalled in they removable head 3l (a friction-less bearing may be provided at this point) and is further provided with a stud shaft 55 which extends through the shaft sealv 3L and has keyed thereto a gear 5i which is held in place thereon by a lock nut 52.

A gear 53 mounted for free rotation upon the trunnion or stud shaft I2 and held thereon by a lock nut 55 is adapted to mesh with a stationary sun gear 56 mounted on the end supporting casting. 26- and forms in part the driving medium for the impellers 35. Idler gears 5l and 58 mountedon a stud shaft 59 journalled in a bearing 60 cast integral or otherwise secured to the head 28 of the housing Ill are provided and complete the gear train between the impeller gear le and the sun gear 56.

A gear 5d mounted for free rotation upon the trunnion or stud shaft I I and held thereon by a lock nut 5I is adapted to mesh with a stationary ring gear 62 mounted in the end supporting casting 25 and forms in part the driving medium for the impeller cage 33 and its associated impellers 34. dler gears I3and 55 mounted on -a stud shaft 65 journalled in a bearing 56 cast integral or otherwise secured to the removable head 3i) of the housing Ill are provided and complete the gear train between the impeller cage 33 and the ring gear 62.

The pumped medium enters the pump through a central bore 61 in the main shaft 2| and travels radially outward through passages 68 formed in the arms I5 of the spiders I'I, thencemtp the pump housing I0 through a passage 69 where it is directed to the first stage of the impeller cage 33. The medium then passes through the impeller 35 through volute passage 'I0 thence through impeller 34 to volute passage 'II positioned diamet- 1 rically opposite volute 15. This procedure is continued until the medium reaches the center of the pump housing where it is directed through a passage I2 to the extreme right of the impeller cage and the same procedure takes place only in a reverse direction, i. e., the medium is forced to travel under pressure from right to left to ward the center of the housing where it emerges into passage 'I3 thence to radial passages 'I4 formed in the arms I6 of the spider I8 to central bore l5 in the main shaft 22 where it emerges under high pressure.

As shown, the ilowv through the stages is so arV ranged that the end thrust on the separating walls of the impellers 3G and 35 is equalized and there is no net thrust.

It will be readily understood from the foregoing descriptionl and particularly from Figure 3 of the drawings that the arrangement of shaft seals will` prevent any possibility ofleakage' of the pumped medium, thereby providing a closed system essential to the operation of such a pump.

With the impeller driver gears 53 and 54 in mesh with the stationarysun and ring gears 56- and 62 secured to the supporting castings 25` and Z.:- 26, and the assembly thus described, rotated rapidly as a unit by means'of` a gear T6A fixed tothe main shaft 2| driven by any suitable prime mover, the housings I0 will revolve in anorbit about the axis of ther main shafts 2I` andV 22' and 1= the impellers 34 and 35 mounted therein will" rotate at high speed inY opposite directions with respect to one anotherv simultaneouslywith the revolution ofthe housings, thereby attaining a high periphericalvelocity with resultant high pressure head due to centrifugal action, while keeping the diameter and Weight ofthe pressure Vessels to a minimum.

Principle of' operation AS shown diagrammatically in Figure 10,. asv

about center B, being drivenby a.. gear` which.

meshes with axed. gear G1. at point D. Itwill be evident that. the peripheral velocity of the.

rotor or impeller R1, at point D, in. space, isizero since, at this point it isheld fixed; by themesh.-v

ing gear. Thus, if crank C has. a.peripheralvee` locity Vi at D, the velocity of the, rotor Ri will have no. pressure. .Point D thus becomes the instantaneous center of rotation of the pumped` medium. At point4 B the rotor speed and` pe;-Y ripheral velocity V3 equals the pump housing Ve,- locity at that point. At point F the rotor velocity in space equals the sum of its own velocity V2 about center B plus the velocity V4 of the pump housing at4 point F; about center A.4 Thus a pumped medium at point F has an instantaneous velocity equal to the sum of velocities about centers A and B at radius'AF, namely V2 plus V4. It will be evident that there will be a flow of the pumped medium witha resultant increase in pressure from point Dto F.

As shown in Figure 1-1`-, as crank and rotating pump housing C rotates in a counter-clockwise direction about center B, being driven by a gear which meshes with a xed gear G2 at point F. It will be evident that the peripheral velocity of the rotor or impeller R2 at point F will be zero since at this point it is held xed by the meshing gear. Thus, if crank C has a peripheral velocity V4 at F, the velocity of the rotorRz at F will be equal and opposite to it or V5 and at F, rotor R2 will have no pressure. It thus becomes comparable to the instantaneous center of rotation of a pumped medium at point F. At point B the rotor speed and peripheral velocity equals the pum-p housing velocity V3 at that point. At point D in instantaneous velocity of the rotor equals the sum of its own velocity V5 plus the velocity V1 of `crank housing at point D. Thus a pumped medium at point D has an instantaneous velocity equal to the sum of velocities about centers A and B at radius AD, namely V1 plus V5. It will be evident that there will be a iiow of pumped medium with a resultant increase in pressure from F to D.

Figure 12 is a diagrammatic showing of two adjacent impellers or rotors circumferentially offset relative to one another and illustrating the diametrical flow of the fluid medium under centrifugal action when the impellers are moved about an instantaneous point in space.

Thus if the rotors or impellers are alternately arranged to rotate in opposite directions it will be evident that a continuous flow and pressure increase will occur, the pump medium passing from one rotor to the next through suitable passages in the revolving housing where the pumped medium is subject to the pressure caused by the revolution of the housing itself plus that received from the preceding rotor stage.

Multi-stage pump arrangement In order to obtain proper balance it will be desirable to arrange several housing assemblies with their rotors or impellers about the center of rotation of the housings.. These rotors may all be driven by the same fixed gears and with their housings they make possible a compact arrangement for many stages. If placed in series the pumps will deliver high pressure on a relatively light weight and small overall size. Such an arrangement of housing assemblies is shown schematically in Figure 9, wherein the impeller housings |00 are supported on spiders |0| mounted on a main shaft |02 journalled in main bearings |03 carried by end supporting castings |04 and |05. Each of the impeller housings are provided with a plurality of alternately arranged oppositely rotatable impellers similar to the impellers 34 and 35 and are driven by gears |06 arranged on opposite ends of the impeller housings which mesh with the stationary sun and ring gears |01 and |08 carried by the end supporting castings. Fluid is admitted to the pump through a central bore in the main shaft thence to one of the impeller housings through duct |09. The impeller housings are connected in series and the fluid under pressure is transferred from one impeller housing to the next by means of ducts ||0, thence out through duct which is in communication with a central bore in the opposite end of the main shaft |02.

A more elaborate arrangement of this type of pump makespossible a variation in pressure at any given speed, thus enabling the construction of a variable pressure constant speed centrifugal pump which, isshown and described as the preferred embodiment of the invention. To accom-` plish this result it is only necessary to provide a means whereby the radius of rotation of the impeller assemblies about the main shafts can be varied. Wherein the impellers 34 and 35 with their housings l0 are arranged to move through a limited arc about center .r while the entire assembly rotates about the main shafts 2| and 22. The xed gears 50 and S2 drive the impellers through drive gears 53 and 5A and their associated gear trains so that the resultant rotatlon ot the impellers remains constant even though the radius of rotation of the impellers relative to the main shafts 2| and 22 is changed. It will be apparent that as the radius of rotation of the impeller housings about the main shafts is decreased or increased at any given R. P. M., there will be a resultant decrease or increase in delivery pressure. q

The mechanism employed to vary the orbital path of the impeller housings |0 about the main shaft is illustrated to advantage in Figures 5 and 6 of the accompanying drawings, and includes an operating handle Ti which is pivoted at 'I8 to the end supporting casting 25 of the pump assembly and has mounted thereon a manuallyV operated pawl 'i9 adapted to engage a segment 80 cast integral with the pivot 18 and together provide means whereby the adjustment mechanism can be locked in any desired position. A yoke 3| pivoted at 32 to the end supporting casting is pro` vided with arms S3 which are connected to theA operating handle by means of a link 84 and is further provided with depending arms 85 adapted to straddle a grooved collar 85 formed on the outer end of a slidable sleeve 8? splined to the main shaft 2 I. The slidable sleeve 8'! has formed therein spiral slots 83 which are adapted to engage trunnions 89 carried by the hub 99 of a spur gear 9| and provides a loose coupling between the slidable sleeve 8l' and the spur gear 9| which permits free movement of the parts relative to one another irrespective of their rotary motion. A slip ring 92 fits within the groove of v the collar 86 and is provided with trunnions 93 which are journalled in the ends of the depending arms 85 of the yoke 8|.

on the spiders I'I and i8. The shafts 95 are further provided with arms 91 which are connected' to the housings I0 at 98 through links 99.

gear through the spiral slots in the slidable sleeve will advance or retard the spur gear relative to the main shaft causing the segmental gears and their associated shafts to rotate, and through the links coupling the shafts rwith the impeller hous-V ings the latter will move radially outward or inward dependent on the direction of movement of the operating handle, thereby varying the radius of revolution of the impeller housings andf the xed points about the main shaft.

With the arrangement of parts thus described it will be evident that any adjustment varying the orbital path of the impeller housings will beV synchronized to keep the rotating members in proper alignment and that such adjustment can be made at the will of the operator without interfering with the speed of the pump.

The pump housing illustratedin Figures 13ans segmental gears Si!VV adapted to mesh with the spur gear 9| are keyedV to shafts 95 journalled in bearings 96 :formed asaoca 14, includes the essential details provided, in Figcure` 3 or thev preferred formA of the invention and comprises animpeller cage l2ilhaving a plurality of por-.ts i2!` therein, adapted to register with the fluid ducts providedy in therhousing. The-impeller cage is` mounted- `Within the central bore. of, the` housing and is locked against rotation by any sui-table means. Mounted for free rotationA Within the. impeller cage there is provided a. plurality oi impellers 22 spaced apart by discs |23 having a iiuid passage 24. therethrough, the. impellers 22- are keyed to a shaft |25 and are adapted toV rotate therewith while thev discs are held againstv rotation by theV engagementv of the projectionsv L26v formed on. the peripheries thereof with the longitudinal slots IZL provided in the impeller Gage;

-The modified pump illustrated in Figure 15 reduces the pump to its simplest form and com.- prises but a single impeller |28, and the form in Figure 1.6 comprises a duplication of thestructure illustrated in Figure 15.

i It will be understood, that the above description and accompanying drawings comprehend onlyra general embodiment of the invention and that various changes in the construction, proportion, arrangement and general combination of parts may be made without departing from the spirit and scope of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the. invention being indicated by the appended claims rather than by the foregoing description, with all changes. falling within the,

scope, meaning and range of equivalency of the claims-intended to be embraced therein.

The-invention described herein may be manuiacturedand. used by or for the Government. of

the United States of America for governmental.

purposes without the payment of any royalties thereon or therefor.

What is claimed is:

i. multi-stage variable pressure rotary pump including in combination plurality of centri-fugal pump units each comprising a housing hav--y ing apressure cham-ber therein and provided with a uid inlet and a flu-id outlet; a, mach-ine fra-mes; a-suspension shaft revoluble therein; a suction conduit and a discharge conduit formed insaid suspension shaft; a pair of spaced spider membersi'ormed integral-with said shaft; axially alined bearingsiorrned in said spiders; thev legs of, said spiderv members having formed therein radial` duid passages interconnecting said fluid inlets and said fluidoutletsi-n said plump housings.v vif-ithv said suction conduit and said discharge conduitin said suspension shaft; said pump housings each provided with axially alinedv trunnions ec centrically disposed thereto and journalled in said bearings in said spiders; an impeller cage rotatably mounted in each oi said pressurey chambers; said impeller cages havinga plurality of ports formed therein; a driving headcoupledito.

eachof said impeller cages at one end thereof.; a studshait formed thereon; a gear keyed to each of said stud-shafts; an impeller shaft coaxially mounted in each of said im-peller cages having one end extended through the other end of said impeller cages and pump housings; a gear vkeyed to each oi saidlimpeller shafts; a plurality or impellers mounted in each oiV said impeller cages Aand formingya series of interccrnmunicatingpressure stages; certain of said impellers being keyed to said. impeller cagesV for rotationk therewith,` the others being keyed to saidmpeller 8V, shafts for rotation therewithwithinsaid. impeller lcages; a stationary ringl gear mounted in said frame concentric. with respect, to said suspension. shaft; a gear train connecting said impeller cageV gears with said ring gear; a stationary sun. gear mounted on said frame concentric to said. suspensionshait; a gear train connecting said. impeller shaft. gears with. said sun gear; means for r0- tatingsaid suspension shaft to cause Said pump units` to revolve therewith, whereby to cause said impellers, through their respective gear trains in mesh with said stationary ring and sun gears, to` rotate about their axis in each pressure cham-y ber in opposite directions during their revolution about the axis of said suspension shaft to induce. flu-id admitted into said pressure chambersv through` said. suction conduit to flow from stage to stage through said pump units toward said discharge conduitA 'with progressively increasing. pressure; and meansfor adjusting the radial displacement of said pump units from the axis of saidshait by turning them about their tru-nnion hearings to vary the pressure of the fluid medium delivered from said pump units independently of the speed` of operation.

2. A multi-stage variable pressure rotary pump including in combination a pluralityY of centrifugal pump units each comprising a housing having a pressure chamber therein and provided with afluid inlet and a iiuid outlet; a machine frame; a drive shaft including suspension means revoluble therein; said pump units 'being eccentrically journalled in said suspension means in annularly spaced. relation about the axis of said shaft;

means for rotating said shaft-With said pump` uni-ts; a piu-rality of pairs of impellers mounted in each of said chambers and forming a series of intercommunicating pressure stages; means driven by said rotating means for moving the impellers of each of said pairs in opposite directions about a common axis in each of said chambers to cause uid admitted into said chambers through said. inlets to. iiow from stage to stage through said pump units toward said outlets with progressively increasing. pressure; and means for adjusting said pump units on their eccentric journals to vary the pressure of the fluid mediumvde.- lvered from said pump units, comprising a, sliding sleeve having spiraly slots formed therein splined on said drive shaft; a spur gear mounted for free rotation on said shaft; a hub formed on said spur gear having a. central bore therein adaptedto receive said sleeve; trunnicnscarried by-saidhub adapted to t Within saidspiral slots in said sleeve; a shaft for each pump unit carried by said suspension. means; segmental. gears keyed to one end of said shaftsmeshing With said` spur gear.; Vradially extending arms integral with said shafts; a pair of arms formed integral on said pump housings; links connecting said arms of said pump housings to said arms on said shafts; a grooved collar formed on the outer end of` said sliding sleeve; a yoke pivotedy to said frame adapted to straddle said. grooved collar; a slip ringiitted Within said groovein said col--l lar; trunnions carried by said slip ring adapted to be journalled in the ends of said yoke a pair of upwardlyv extending arms formedv on saidyoke; an operating handle. pivoted on. said frame; a link connecting said upwardly extending arms of saidV yoke to said operating handle, and locking means for said operating handle and said adjusting-` 3. AL centrifugal pump lcomprising a rotatable housing `having an ilmpell'er char-nberfeccentrcally located therein, an impeller rotatably mounted in said chamber and having radial passages connected together at their inner ends, pump inlet and outlet passages in said housing connected to the periphery of said chamber in each of the halves thereof respectively which are opposed to each other in a radial direction with respect to the axis of rotation of said housing, driving means for rotating said housing, connections from said driving means for rotating said impeller, whereby a centrifugal pressure differential is obtained at the periphery of said halves of said chamber, causing a flow from said inlet passage to said outlet passage.

4, A centrifugal pump as defined in claim 3, wherein said housing and impeller are driven in the same direction for causing a radially outward now through said impeller with respect to the axis of rotation of said housing.

5. A centrifugal pump` as defined in claim 4, wherein said connections comprise a stationary sun gear mounted on the axis of rotation of said housing, and a planetary gear mounted for rotation with said impeller and meshing with said stationary sun gear.

6. A centrifugal pump as dened in claim 3, wherein said housing and impeller are driven in opposite directions for causing a radially inward flow through said impeller relative to the axis of rotation of said housing.

'7. A centrifugal pump as defined in claim 6, wherein said connections comprise a stationary internal ring gear, and a planetary gear mounted for rotation with said impeller and meshing with said internal ring gear.

8. A centrifugal pump as defined in claim 3, wherein said housing is hingedly mounted on a rotatable support, and means for adjusting the housing about said hinge to vary the radial displacement of said impeller relative to the axis of rotation of said support and thus cause a variation in the centrifugal pressure differential independently of the speed of rotation.

9. A centrifugal pump comprising a rotatable housing having a series of axially aligned impeller chambers eccentrically located therein, an impeller rotatably mounted in each of said charnbers and having radial passages connected together at their inner ends, uid inlet and outlet ports at the periphery of each chamber on its two halves respectively which are opposed in a radial direction with respect to the axis of rotation of said housing, passages in said housing connecting said chambers in series, driving means for rotating said housing, and connections from said driving means for rotating said impellers, whereby a centrifugal pressure differential is obtained at the periphery of each chamber in its opposite halves causing a flow through said series of chambers.

10. A centrifugal pump as dened in claim 9, wherein said impellers are all driven by a com mon shaft.

11. A centrifugal pump as defined in claim 9, wherein alternate impellers are driven in opposite directions, whereby the inlet and outlet ports of consecutive chambers will be on the same halves thereof, requiring short passages to connect said chambers in series.

12. A centrifugal pump as defined in claim 11, wherein the alternate impellers are driven by a common shaft, each of said shafts having a planetary gear mounted thereon as a part of said connections, which further include a stationary sun gear and a stationary internal ring gear mounted on the axis of rotation of said housing, and meshing with said planetary gears respectively.

13. A centrifugal pump as dened in claim 9, wherein said housing is hingedly mounted on a rotatable support, and means for adjusting the housing about said hinge to vary the radial displacement of said impellers relative to the axis of rotation of said support and thus cause a variation in the centrifugal pressure differential independently of the speed of rotation.

14. A centrifugal pump as defined in claim 11, wherein said housing is hingedly mounted on a rotatable support, and means for adjusting the housing about said hinge to vary the radial displacement of said impellers relative to the axis of rotation of said support and thus cause a variation in the centrifugal pressure differential independently of the speed of rotation.

15. A centrifugal pump as defined in claim 14, wherein the alternate impellers are driven by a common shaft, each of said shafts having a drive gear at one end of said housing, a pair of planetary gears mounted on said hinge, each planetary gear being geared to one of said drive gears, a stationary sun gear on the axis of rotation of said support meshing with one of said planetary gears, and a stationary internal ring gear on the same axis meshing with the other of said planetary gears.

16. A centrifugal pump as defined in claim 15, having additional housing similarly mounted on additional hinges on said support at circumferentially spaced intervals for common operation by a single sun gear and a single ring gear, the series of chambers in all the housings being connected in series by passages through said support connecting the outlet port of the last charnber in one series to the inlet port of the first chamber in the next series; and connecting linkages between said adjusting means for simultaneous adjustment of all said housings about their hinges.

CALVIN M. BOLSTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 20,880 Hibsch July 13. 1858 507,445 Mortier Oct. 24, 1893 1,511,517 Henderson Oct. 14, 1924 2,183,195 Kane Dec. 12, 1939 2,201,099 Roe May 14, 1940 2,374,122 Nelson Apr. 17, 1945 FOREIGN PATENTS Number Country Date 399,619 Great Britain Oct. 12, 1933 478,960 Germany July 1.0, 1929 

